Python:最长子列表的长度? [英] Python: Length of longest sublist?

问题描述

可能重复:
Python在列表中选择最长字符串的最有效方法?

Possible Duplicate:
Python’s most efficient way to choose longest string in list?

我有一个清单L

L = [[1,2,3],[5,7],[1,3],[77]]

我想返回最长子列表的长度而不需要遍历它们，在本例中为3，因为[1,2,3]是长度3，并且是四个子列表中最长的.我尝试了len(max(L))，但这不能满足我的要求.有什么方法可以做，还是循环是我唯一的方法?

I want to return the length of the longest sublist without needing to loop through them, in this case 3 because [1,2,3] is length 3 and it is the longest of the four sublists. I tried len(max(L)) but this doesn't do what I want. Any way to do this or is a loop my only way?

推荐答案

max(L,key=len)将为您提供长度最长的对象(在您的示例中为[1,2,3])-实际获取长度(如果您在乎的话)关于)，您可以执行len(max(L,key=len))，这有点丑陋-我将其分成2行.或者，您可以使用ecatamur提供的版本.

max(L,key=len) will give you the object with the longest length ([1,2,3] in your example) -- To actually get the length (if that's all you care about), you can do len(max(L,key=len)) which is a bit ugly -- I'd break it up onto 2 lines. Or you can use the version supplied by ecatamur.

所有这些答案都有循环-在我的情况下，循环是隐式，这通常意味着它们将在优化的本机代码中执行.如果您考虑一下，不看每个元素怎么会知道最长的元素?

All of these answers have loops -- in my case, the loops are implicit which usually means they'll be executed in optimized native machine code. If you think about it, How could you know which element is the longest without looking at each one?

最后，请注意，key=function不是特定于max的功能.许多python内置函数(max，min，sorted，itertools.groupby，...)使用此特定的关键字参数.绝对值得花一点时间来了解它的工作原理和通常的功能.

Finally, note that key=function isn't a feature that is specific to max. A lot of the python builtins (max,min,sorted,itertools.groupby,...) use this particular keyword argument. It's definitely worth investing a little time to understand how it works and what it typically does.

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